What are the influencing factors of powder metallurgy heat treatment?

What are the influencing factors of powder metallurgy heat treatment?

In our daily life, the application of powder metallurgy is very extensive. It plays an important role in the fields of automobiles, hardware, household appliances, communications, medical devices, etc. In the manufacturing process of powder metallurgy, heat treatment is one of the most important processes, and its quality will directly affect the quality of powder metallurgy products to a certain extent. Do you know what are the influencing factors of powder metallurgy heat treatment? Here is a brief introduction of the Zhongwei Precision Editor:

powder metallurgy

The influencing factors of powder metallurgy heat treatment are as follows:

1. Effect of porosity on heat treatment process

During the heat treatment of powder metallurgy materials, the rapid cooling can inhibit the diffusion of austenite into other structures, so as to obtain martensite. The existence of pores has a great impact on the heat dissipation of materials. Through the thermal conductivity formula: thermal conductivity=theoretical thermal conductivity of metal × (1-2 × Porosity)/100

It can be seen that the hardenability decreases with the increase of porosity. On the other hand, porosity also affects the density of the material, and the effect on the surface hardness and hardening depth of the material after heat treatment is related to the density, reducing the surface hardness of the material. Moreover, because of the existence of pores, salt water cannot be used as the medium during quenching to avoid corrosion caused by salt residue. Therefore, general heat treatment is carried out in vacuum or gas medium.

2. Effect of Porosity on Surface Hardening Depth during Heat Treatment

The heat treatment effect of powder metallurgy materials is related to the density, permeability (hardenability), thermal conductivity and electrical resistance of the materials. Porosity is a very big reason for these factors. When the porosity exceeds 8%, the gas will rapidly penetrate through the pores. When carburizing and hardening, the effect of surface hardening will be reduced by increasing the carburizing depth. Moreover, if the carburizing gas penetrates too fast, soft spots will be produced during quenching, which will reduce the surface hardness and make the material brittle and deformed.

3. Effect of Alloy Content and Type on Powder Metallurgical Heat Treatment

Copper and nickel are common alloy elements, and their content and type will affect the heat treatment effect. The hardening depth of heat treatment increases with the increase of copper content and carbon content, and decreases when it reaches a certain content; The stiffness of nickel alloy is higher than that of copper alloy, but the inhomogeneity of nickel content will lead to the inhomogeneity of austenite structure.

4. Effect of High Temperature Sintering

Although high temperature sintering can obtain good alloying effect and promote densification, different sintering temperatures, especially at low temperatures, will lead to a decrease in heat treatment sensitivity (decrease in alloy in solid solution) and mechanical properties. Therefore, good heat treatment effect can be obtained by using high temperature sintering with sufficient reduction atmosphere.

The above contents are the influencing factors of powder metallurgy heat treatment. Its powder metallurgy heat treatment process is a very complex process, which is related to porosity, alloy type, alloy element content and sintering temperature. Compared with compact materials, its internal homogeneity is poor. To obtain higher hardenability, it is necessary to increase the complete austenitizing temperature and extend the time. Uneven austenitic carburizing can obtain a high carbon concentration that is not limited by the saturated carbon concentration of austenite. In addition, the addition of alloy elements can also improve the hardenability. Steam treatment can significantly improve its anti-corrosion performance and surface hardness